In this work, it is experimentally shown that the etching of GaN or InGaN NWs in the KOH solution allows managing the morphology and optical properties of the nanowires array. Thinning rate of GaN nanowires is 5 times slower than the rate for InGaN nanowires along semi-polar and non-polar direction for nanowires with Ga-polar crystal structure. The diameter of the InGaN NWs decreases from 200-100 to 30-40 nm. After etching process, the intensity photoluminescence (PL) of nanowires and uniformity PL signal at all sample area increase.